A rotating piston machine is known (DE-38 25 354 A1) which is made with rotary valves which have the same rpm and thus necessarily a diameter roughly the same as the annular cylinders. The rotary valve fits from the outside into the annular cylinder, by which the box dimension roughly corresponds to twice that of the annular cylinder or the rotor disk diameter. The fresh gas flows are deflected by 180 degrees in front of the piston in order to be able to initiate ignition and expansion behind the piston.
Conversely, the object of this invention is to devise a rotating piston machine with rotating pistons in which the gas flows need not be deflected, so that pulsating motion is avoided.
The engine according to the invention contains one or more annular cylinders with a round cross section which is preferably circular. In the annular cylinder are at least two rotating pistons with a cross section which is matched to the cross section of the annular cylinders which are located on the periphery of a rotor disk, preferably at the same angle to one another. The annular cylinder is divided by disk cams which are made as rotary valves into several cylinder chambers, of which at least one is an expansion chamber. At least one other cylinder chamber can be an intake compression chamber.
Instead of an intake compression chamber, there can also be an external compressor which routes the gas mixture directly from the outside into the expansion chamber. In doing so, in front of and behind the piston or pistons only the working steps which are carried out in the expansion chamber can take place. The compressor handles intake and compression. In addition, there can be cylinder chambers as hydraulic and/or pneumatic pumps. In the embodiment with the intake compression chambers each expansion chamber contains at least one overflow channel which discharges with its one port into an intake compression chamber and with the other port into the expansion chamber. The expansion chamber furthermore contains at least one exhaust channel, the intake compression chamber at least one air intake channel.
In the embodiment with the intake compression chambers the overflow channel is arranged such that with one of the rotary valves via one control recess the gas column in the overflow channel and with another control recess the piston passage between the intake compression chamber and the cylinder chambers can be controlled.
One air intake channel discharges into one cylinder recess in the intake compression chamber, the exhaust channel discharges in the expansion chamber via a cylinder recess.
Compared to known rotating piston machinery, the engine according to the invention has fewer wearing parts and thus lower friction losses. It does not require internal oil lubrication between the inside wall of the cylinder and the outside wall of the piston since it is unnecessary to use piston rings. Gaskets where the rotor disks fit into the cylinder wall and gaskets on the rotary valves can generally be abandoned.
The gas flows always maintain the same direction in both compression and expansion. In the embodiment with intake compression chambers, when the pistons move from the intake compression chamber into the expansion chamber the fresh gas is retained in the overflow channel until the piston has moved from the intake compression chamber into the expansion chamber and is then ignited in the expansion chamber behind the receding piston. Thus cylinder flushing and gas exchange can be almost 100%; in none of the existing internal combustion engines with closed compression spaces was this possible. Because the gas flows always move in the direction of rotation and the pistons likewise divide the cylinder walls in the direction of rotation, at the same time one working step is completed in front of and behind the piston, in the intake compression chamber at the same time fresh gas being aspirated behind the piston and fresh gas being compressed in front of the piston, while in the expansion chamber at the same time ignition takes place behind the piston and the gas is expanded and expelled and residual gases burned in front of the piston are ejected by the preceding stroke. This enables optimum cylinder flushing.
In the engine according to the invention much shorter pistons are possible than in engines of the prior art, for example in DE-38 25 354 A1. Thus it is possible to provide shorter control recesses in the rotary valves, with which shorter opening and closing times of the rotary valves are connected. The rotary valves can rotate with higher rpm than the rotor disk, for example with twice the speed, and they can then have a smaller diameter. If in addition two rotary valves which turn in opposite directions and which lie parallel on top of one another are used as rotary valve pairs, the opening and closing times of the control recesses can again be cut in half.
If the number of pistons and cylinder chambers are increased while the cylinder volume remains the same, the power density increases at the same time, as does the smoothness of running, since the expansion thrusts increase and are distributed more uniformly in the annular cylinder. The number of expansion chambers times the number of pistons corresponds to the number of expansion strokes (equal to the working strokes) when the rotor disk turns 360 degrees.
If an engine version with two or more cylinder chambers is used, the cylinder chambers which are not needed for the ICE can be used as assemblies for producing hydraulic and/or pneumatic pressure and/or suction or vacuum. Likewise the rotor disks or pistons can be driven in the direction of rotation if the hydraulically and/or pneumatically used cylinder chambers receive the corresponding pressurized medium from the outside via the intake channel, for example, as a starter for the starting phase.
In the engine according to the invention, grinding seal rings and/or piston rings can be largely abandoned. Since no component of the engine executes rotary motion, damaging mass forces can be avoided. Rotation occurs in only one direction. Mushroom valves with hammering stress of valves and valve seats which at the same time prevent unhindered gas flow need not be used.
Thermodynamics at least equivalent to the straight cylinder space of the reciprocating piston prevails in the bent cylinder space of the annular cylinder.
Inherent sealing elements are unnecessary. If they are used at all, preferably materials with very hard surface structure and low coefficients of expansion, for example teflon or ceramic, are used. To seal the pistons to the inside wall of the cylinder, so-called gas pressure labyrinth seal lubrication is used. Here the high combustion pressure which can exceed 200 bar is used through the corresponding holes and routed areas in the piston in order to press a small part of the burning gas mixture between the inside wall of the cylinder and the piston. In doing so air cushions are formed which are used both as lubrication and also to minimize gas loss on the pistons. For most applications however a seal with a very small gap between the piston and inside wall of the cylinder is enough.
By means of the pressure of the combustion gases and/or the compressed fresh gases different engine bearings can be made as aerodynamic bearings. In particular, the rotor disks where they fit into the annular cylinder wall, the rotary valves to the housing, and for rotary valve pairs working in opposite directions the rotary valves can also be supported or lubricated to one another by gas pressure support.
For this reason only the corresponding openings or recesses are necessary. By way of replacement for the rotor disk and rotary valves, as above, water instead of lubricant can be introduced through the corresponding holes; at the operating temperature the water becomes steam and thus a corresponding pressure for pressure support is achieved.
The number of individual parts and sealing elements used is less than in comparable designs. The combustion space at the instant of ignition is as close as possible to the ideal shape of a sphere, at least to a cylindrical shape, by which combustion is complete and the proportion of unburned gases in the exhaust remains as small as possible.
In the engine according to the invention there is clear separation of the propulsion and working spaces. For a very small box dimension a favorable power-weight ratio and high power density can be achieved. No special machinery need be built to produce the engine, as is necessary for example in Wankel engines. All parts can be produced with known machine tools. Since also all additional assemblies, such as the starter, generator, exhaust, carburetor, injection system and so forth can be series produced parts, additional development costs are avoided. The engine structure is simple, it contains few wearing parts such as seal rings, and no oil is necessary for lubrication of the inside cylinder walls. This prevents high maintenance and the corresponding costs. Any liquid and gaseous fuels can be used, resulting in low operating costs. Since no lubricating oil need be used, changing the oil is superfluous for most applications.
Additional injection of finely atomized water into the combustion space can also be used to increase engine output or to save fuel.
At the combustion temperatures which occur in the combustion space, exceeding 1000.degree. C., the water explosively becomes steam and thus increases its volume by several fold--compression is increased--but at the same time combustion of the fuel-gas mixtures can be influenced (lowering of the octane number).
In reciprocating piston engines which work against top and bottom dead center of the pistons, this can lead to much higher material stress and thus to much higher maintenance costs, shorter service life of the engine and to much higher manufacturing costs.
In the engine according to the invention all the advantages of water injection can be used without the need to tolerate disadvantages. Because combustion always takes place behind the receding piston, soft combustion always takes place regardless of which fuel and what compression or rpm are being used.
Since very high compression is easily possible, turbochargers or other compressors can be used. In this way the engine according to the invention can have an extremely high power density.
To facilitate starting, in the intake or compression part there can be a decompression valve. Since the engine according to the invention has a lower inherent braking effect when the accelerator lever is pulled back than a reciprocating piston engine, there can be a throttle valve in the exhaust line or intake line of the engine.
This invention combines the advantages of a reciprocating piston engine with the advantageous properties of the turbine and can so to speak be classified in the middle between the two known designs. The most important feature is the gas exchange according to the reciprocating piston principle in the closed space. In this way it can be used as a motor vehicle and aircraft engine and also for helicopters.
Not only due to high power density and small box size, but also the simultaneous possibility of use as a hydraulic and/or pneumatic pump and/or drive, the engine according to the invention can be very easily be used in many areas where internal combustion engines, hydraulic and pneumatic pumps and drive systems are used. Very low production costs, low maintenance costs and low operating costs further expand possible applications.
The engine according to the invention avoids complicated and noisy valve drives and the fatigue limit stress on gear parts, crankshaft and connecting rods, which limits rpm in conventional reciprocating piston engines. Also the disadvantages of turbines, such as sluggish control behavior, poor exhaust gas quality and poor efficiency, which limits their use as motor vehicle engines to a few special cases such as large vehicles, tanks and the like, are prevented with this invention. With the engine according to the invention it is not a problem to reach high rpm. In it the maximum rpm is limited not by the allowable fatigue limit of gear parts, but only by the combustion speed of the fuel used, which is generally 20 to 30 m/s.
In one embodiment of this invention the engine consists of an annular cylinder (torus) in which at least two pistons with a cross section which corresponds to the diameter of the annular cylinder rotate. The pistons are attached on the periphery of a driver plate (rotor disk) in a suitable manner, such that in spite of the centrifugal force they do not rub against the inner outside contour of the annular cylinder. Although pistons with commercial piston rings can be sealed against the cylinder wall, the use of materials with a very hard surface structure and low coefficient of expansion and a very small gap between the pistons and the inside wall of the cylinders is sufficient. If a seal as tight as possible is necessary for the application, gas pressure labyrinth seal lubrication can be provided. Since the pistons run without contact and friction and without oil, wear on cylinder walls and pistons is eliminated. No oil combustion residues reach the exhaust gas, and no carbon deposits form on the piston bottoms or ignition equipment. Operation is quiet and service life is increased since the internal friction is greatly reduced. The major increase of friction losses with rpm, as is known in reciprocating pistons, is prevented in the rotating pistons used according to the invention. In a hot reciprocating piston engine at compression of 1:10 losses due to piston and piston ring friction alone can be 50 to 60% of all internal friction and they are completely eliminated with the rotating piston used according to the invention. Fuel consumption is minimized, and exhaust quality optimized.
In another embodiment without an intake compression chamber the fresh gas compressed by the compressor is retained in the intake channel against the rotary valves when the pistons move from one expansion chamber into the next and then is ignited and expanded behind the receding piston and against the closed rotary valve.
The danger of removal of the oil film by fuel condensation which occurs when a piston engine is started cold is avoided, because an oil film in the cylinder is no longer necessary. The oil-free cylinder also allows use of the engine in dusty, dry combustion air, for example in the steppes or desert, because the dust is blown through the cylinder without adhering to the cylinder wall.
The inside wall of the annular cylinder need not be made wear-resistant. At the same time a certain degree of roughness of the inside wall of the cylinder, for example due to tool marks, is desirable because the surface roughness reduces leakage losses through the gap between the pistons and cylinder wall since the roughness reduces the gas velocity in the narrow gap. The cylinders are therefore preferably not ground from the inside.
The gas pressure labyrinth pistons preferably used contain in the piston bottom a thin central blind hole which on its end passes into even thinner transverse holes which emerge laterally from the piston. The weak counterpressure which occurs here counteracts leakage losses so that a sufficient seal is ensured. It is known anyway that sealing of machine components which move relative to one another can only ever cause "technical tightness", but never absolute tightness. The "blow-by" of hot combustion gases which is feared by engine designers does not occur in the rotating piston used according to the invention because the rotating pistons recede before the heat front and in high frequency migration of the heat-stressed sites on the annular cylinder wall in the direction of rotation "blow by" cannot occur at all. Nor would it be harmful since the combustion gases would simply reach to in front of the pistons and would be pressed by them into the exhaust channel and thus into the exhaust.
The number of pistons, cylinder chambers and rotary valves is preferably the same. They are preferably each arranged at the same angle to one another. In the embodiment with the intake compression chambers during each revolution the four "strokes" of the ICE are carried out as frequently as the product of the number of pistons.times.the number of expansion chambers. This means that in an engine version with four pistons and four cylinder chambers, of which two are made as expansion chambers, in one annular cylinder ignition takes place (2.times.4) equals 8 times, in the two expansion chambers ignition always taking place at the same time. Each of the four pistons compartmentalizes the four cylinder chambers once at a time. Therefore, for rotation of 360.degree. four times the annular cylinder volume is used. The usable working volume for a 360.degree. revolution is a multiple of the actual annular cylinder volume, specifically the piston or cylinder chamber number.times.the actual volume of the annular cylinder. This multiple use of the annular cylinder volume is not possible in any other internal combustion engine with closed combustion spaces.
The problem of diverting the fresh gas behind the rotating piston which is compressed in front of the piston, a problem which is difficult to solve in all rotary machines, is solved as follows in the embodiment with intake combustion chambers: The fresh gas is retained in the overflow channel or in the intake channel when the piston moves from the intake compression chamber into the expansion chamber until the piston has run through the rotary valve recess and is then ignited in the expansion chamber behind the receding piston. The annular cylinder is divided by the rotary valves into at least two cylinder chambers, into one expansion chamber and one intake compression chamber. In machines with more than two cylinder chambers there can also be at least one hydraulic chamber and/or one pneumatic chamber. The number of pistons, cylinder chambers and rotary valves or rotary valve pairs is preferably the same, they are located on the same plane, preferably at the same angle to one another.
In the embodiment with intake compression chambers, at the end of one intake compression chamber at a time and at the start of one expansion chamber there are recesses in the cylinder wall which are joined to one another by an overflow channel. One rotary valve with the corresponding rotary valve recesses fits in the overflow channel. The part of the overflow channel or the intake channel which, viewed from the rotary valve, is located on the side of the expansion chamber is preferably used at the same time as the combustion space with the expansion chamber. The piston is preferably longer than the overflow channel so that it can close the latter briefly upon passage. The ignition device is preferably located in the overflow channel behind the rotary valve or in the expansion chamber of the annular cylinder.
On its front and/or back the piston can preferably have a projection which is shaped such that it is matched to the advancing rotary valve opening so that the piston can enter the rotary valve opening even before the annular cylinder cross section is completely cleared. Likewise it can emerge again when the opening closes. The volume of the projections on the one hand reduces the compression space in front of the still closed rotary valve and thus increases the compression of the fresh gas upon entry into the overflow channel. Secondly, the piston is prevented from pushing or entraining the gas mixture or liquids from one cylinder chamber into the next one. The openings for the intake and exhaust channel are preferably, as in a two-stroke reciprocating piston engine, always opened. They require no mechanical control and are briefly washed and thus closed only by the rotating piston.
The invention is detailed below using the Figures by way of example.